When the Actual World Is Not Even Possible

Abstract

Approaches to quantum gravity often involve the disappearance of space and time at the fundamental level. The metaphysical consequences of this disappearance are profound, as is illustrated with David Lewis’s analysis of modality. As Lewis’s possible worlds are unified by the spatiotemporal relations among their parts, the non-fundamentality of spacetime—if borne out—suggests a serious problem for his analysis: his pluriverse, for all its ontological abundance, does not contain our world. Although the mere existence—as opposed to the fundamentality—of spacetime must be recovered from the fundamental structure in order to guarantee the empirical coherence of the non-spatiotemporal fundamental theory, it does not suffice to salvage Lewis’s theory of modality from the charge of rendering our actual world impossible.